Conventional emulsions are typically formed when a liquid phase is dispersed in another immiscible liquid phase, e.g., oil in water or water in oil, and the dispersion is stabilized against coalescence by a steric and/or electrical barrier (e.g., surfactant) at the interface between the dispersed phase and the continuous phase.
Emulsions of the subject invention, on the other hand, are so-called aqueous-aqueous emulsions in which both the dispersed phase and the continuous phase are aqueous in nature. Such aqueous-aqueous emulsions do not have the “heavy oil” feel associated with conventional emulsions formed by oil and water. Further, since the dispersed phase is aqueous, highly water soluble benefit agents (e.g., glycerin, proteins) can be integrated or encapsulated in the dispersed phase offering potential of high delivery efficiency to skin or other substrate from a wash off product. Because the dispersed phase is typically and preferably poor in surfactant (for example, less than 5% by wt.), bioactive agents such as proteins also have a better chance to preserve their native structures in such aqueous-aqueous emulsions.
U.S. Pat. No. 6,429,177 to Williams et al. discloses aqueous-aqueous biphasic compositions comprising surfactant, thickener (e.g., hydrophobically modified polyethylene glycols such as PEG (160) sorbitan triisostearate), polyalkylene glycol and chelating salt to induce phase separation. This reference discloses biphasic liquids rather than stable aqueous-aqueous emulsions of the invention and further fails to define how the stable emulsion of the invention would be formed or what they are made of.
Applicants have also filed two co-pending applications entitled “Biphasic Composition Induced by Polydextrose” to Patel et al.; and “Biphasic Composition Induced by Polydextrose and Sucrose” to Pereira et al., both filed on Aug. 14, 2002. These disclose use of polydextrose to induce biphasic liquids and fail to disclose the stable aqueous-aqueous emulsions of the objection. They further fail to disclose how to form such emulsions and what they are made of.
Finally, U.S. patent application Publication No. U.S. 2002/0055461 A1 to Jin et al., published May 9, 2002, discloses a stable polymer aqueous-aqueous emulsion system. This reference requires use of a third charged particle phase that is critical because it coats the dispersed phase and provides an electrical barrier to prevent the coalescence of the dispersed phase. In the subject invention, the disclosed aqueous-aqueous emulsion is formed by surfactant and a molecule (defined by specific water solubility and MW) upon mixing with water and no additional emulsifier is required. The reference fails to teach specific dispersed phase molecule and surfactant or surfactant system of continuous phase of the subject invention.